A positive association between consanguinity and fertility in communities of Paraíba, Northeast Brazil

Consanguinity of human populations can but does not have to be associated with increased fertility. A recent study involving communities of Northeast Brazil revealed increased levels of endogamy.Data from 20 451 interviewed couples and their 74 289 children were analysed.The present study aimed to compare fertility between consanguineous and unrelated couples of these communities.Consanguineous and unrelated couples of the 39 communities had an average of 4.3 (SD = 0.9) and 3.5 (SD = 0.8) children (p 0.0001), respectively. Average offspring number of consanguineous couples varied from 3.9 (SD = 1.1) to 5.6 (SD = 3.4) for couples related at the level of third cousins and double first cousin/uncle-niece, respectively (p 0.005). The correlation coefficient between Human Development Index and fertility was -0.38 (p = 0.0179) and -0.23 (p = 0.17) for unrelated and related couples, respectively.Results indicated an overall positive association between consanguinity and fertility. Fertility tended to be increased, for closely related couples, compared to those related more distantly.